The present invention relates to a signal processor and a control apparatus and relates to, for example, a signal processor and a control apparatus used to control a motor.
A resolver that detects a rotation angle from variations in a magnetic field due to a rotation of a rotor is known as a rotation angle sensor.
Japanese Unexamined Patent Application Publication No. 8-287173 and Japanese Unexamined Patent Application Publication No. 8-35856 disclose a method of shifting a phase of one of two-phase resolver signals obtained by single-phase excitation by 90° by a signal processor, synthesizing the resulting signal with the other one of the two-phase resolver signals, and detecting an angle of a resolver from the synthesized signal. Further, Japanese Unexamined Patent Application Publication No. 2004-347612 discloses an apparatus that detects whether there is an abnormality in a detected angle of a resolver.
According to the aforementioned methods, when a rotor of the resolver is rotated, the phase shift amount by a phase shifter is deviated from 90°, which causes a larger error in the angle to be detected.
Another technique for shifting the phase of the resolver signal includes a resolver digital converter (RD converter). The RD converter detects a signal synthesized from resolver signals with two-phase outputs and a carrier signal that excites a resolver through synchronous detection and feeds back an amount of shift of the phase from the detection signal to perform tracking.
In the apparatuses that detect the angle of the resolver according to related art, however, a signal processor that improves the resolution of the phase detection without increasing the clock frequency of the controller or decreasing the frequency of the excitation signal is not achieved.
The other problems of the related art and the novel characteristics of the present invention will be made apparent from the descriptions of the specification and the accompanying drawings.